Hello Space Fans and welcome to another edition of Space Fan News.
In this episode astronomers at the European Southern Observatory have observed an exoplanet
that is tidally locked around it’s star and because of this has extreme temperatures
on the daytime and nighttime side.
The temperatures are so hot that on the day side, iron is a gas and at night that gas
condenses into molten iron rain.
It seems the more we look for and at exoplanets, the stranger some of them become.
We tend to be really focused on the Earth-like ones because we like to fantasize that somehow,
someday we could live on one of those.
But Earth-like planets are elusive compared to all the others that are out there and this
week, astronomers using ESO’s Very large Telescope and associated instruments have
found a really strange exoplanet.
The planet is called WASP-76b and it orbits its star WASP-76 once every 1.81 days.
That’s its year folks!
The system is located some 640 light years away in the areas of the sky bounded by the
constellation Pisces.
WASP-76b itself is what astronomers call a hot-jupiter, meaning its about the size of
jupiter and, well, it’s hot.
It’s about1.8 times larger in radius than Jupiter and is a little less massive (about
.9 times the mass of Jupiter).
Now a really large planet the size of Jupiter going around it star once every couple of
days is strange enough but because it’s year is so short, that also means it’s pretty
close to the star, which makes it very hot.
Being so close also grabs it pretty strongly to the star.
WASP-76 is an F7 star that is about 1.7 times bigger than our sun and 1.5 times as massive
and because of all these factors, WASP-76b is tidally locked to the star in its orbit
around it.
Tidally-locked means that the rate at which the planet rotates matches its orbit around
the star making one side of the planet always facing the star and the other side facing
away.
So here we have a planet that’s way bigger and more massive than Jupiter, going around
an F7 star - which are known to, among other things, emit large amounts of UV radiation
- going around that star every couple of day AND it has one side always facing the star
and the other facing away…
Well that’s a party where you know weird stuff’s gonna happen.
Astronomers looking at this system using ESO’s VLT and specifically the spectral imager known
as ESPRESSO, a fiber optics high resolution spectrograph, and when they looked at the
planet at various spots in the transit (that’s the part where the planet passes between us
and the star), on the day side of the planet where temperatures were around 2400K, which
means the daytime side of this star is comparable to some of the cooler stars out there.
Looking at the spectral images, they were able to closely follow the neutral iron in
the atmosphere as the daytime on the planet progressed.
Because different parts of the planet were visible to us as the planet went around and
correcting for all the motions of the planet rotation and orbital motion, the team look
at what was happening to the iron content in the atmosphere.
They noticed that when they could see more of the daytime-side disk, they say more Iron
and because we’re talking about 2400K, it had to be gaseous.
Then looking at the evening terminator as it became less visible but was still there,
the iron content went down and on the dark side of the planet and the morning terminator,
they couldn’t see any iron.
So they concluded that since they could see neutral iron on the dayside and the evening
terminator, but not the nightside and the morning terminator, the gaseous iron in the
atmosphere condensed as it moved to the night side (or the dark side as I like to say) and
since the nighttime temps are still pretty hot, of around 1600k, that’s still hot enough
for iron to be a liquid.
And it rains.
Iron.
Molten Iron.
Here’s what they think that would look like.
This is iron condensing into rain.
This wasn’t in the paper but it makes me wonder about the oceans on WASP-76b.
Would need a helluva boat to sail on molten seas.
Or maybe it’s like a giant version of Mustafar system in Star Wars.
Who knows, we could have just found the birthplace of Darth Vader.
Alright enough of that.
I want to thank all Deep Astronomy Patreon Patrons who keep these episodes coming and
I want to thank all of you for watching and as always Keep Looking Up!